When a semiconductor integrated circuit (IC) is mounted onto a circuit board, conventionally leads provided on the sides of the IC package are inserted into through-holes provided in lands of a circuit pattern on the circuit board and soldered to electrically connect to the lands. The numbers of input and output terminals of ICs have increased with the increase of the integration densities of ICs in these years. In addition, the operating frequencies of ICs have also increased. Along with the demand for high frequency characteristics has come growing demand for high-density mounting on circuit boards, short-distance interconnections, and finer pitches.
In these circumstances, a technique has been proposed in which input and output terminals are arranged in a grid array on the bottom surface of an IC package and an interposer is used to mount the IC package onto a circuit board in order to efficiently arrange the input and output terminals. An interposer is a thin high-terminal-density connector in which holes corresponding to input and output terminals arranged in a grid array of an IC package are provided in a sheet of insulating material and conductors (connectors) that conduct electricity between both surfaces of the sheet of insulating material are inserted in the holes. Terminals are also provided on the circuit board in the similar grid array pattern.
Japanese Laid-open Patent Publication No. 2006-66407 discloses elastic connectors employing silicon spring electrodes. Japanese Laid-open Patent Publication No. 2001-176580 discloses an elastic connector in which wires formed in zig-zags, pleats or coils are incorporated in buttons made of an elastic material. JP-A-2001-176580 also discloses metal springs may be used instead of the wires.
However, the structure that uses silicon spring electrodes to make connecters elastic has a problem that the silicon spring electrodes have high electrical resistance. The configurations in which zig-zag, pleat or coiled wires or metal springs are incorporated in elastic main bodies have a problem that they are physically difficult to miniaturize.